Crimped sleeve to tube joint

ABSTRACT

A sleeve to tube joint is provided of enhanced resistance to pressure loading and which can be enployed with relatively large diameter pipes, in which the sleeve and tube are crimped to each other by diametrically opposite crimps extending concavely inwardly of the outer surface of the sleeve and convexly inwardly of the inner surface of the tube, the respective crimps being isolated from each other by struts extending parallel to the longitudinal axis of the sleeve and tube, provision being made for equalization of the stresses produced in a seal ring contained in an annular flange of the sleeve during compressive reduction of the annular flange, provision also being made for the axial movement of the sleeve relative to the tube during compressive reduction of the flange.

This is a continuation-in-part of copending application, Ser. No.285,498 filed on Dec. 16, 1988, and now abandoned.

FIELD OF THE INVENTION

This invention relates to joints for piping systems in which a sleevecontaining a sealing member is permanently crimped onto a plain endedunthreaded pipe end in a manner preventing disconnection of the sleevefrom the pipe, other than by destruction of the joint. The sleeve can bea double ended with two sealing members for interconnecting one pipewith another, or, it can be part of a fitting of any form which has beenformed integrally with or joined to that end of the sleeve which is toproject beyond the end of a pipe.

While not limited thereto, the crimped joint of the present inventionfinds particular application in crimped sleeve to tube pipe joints usedin connection with relatively thin walled metal pipe.

BACKGROUND OF THE INVENTION

Crimped sleeve to tube pipe joints as presently known, are well known inthe art, and because of significant advantages of the concept havegained acceptance for many uses.

Tube joints of this general type were first conceived of and describedin U.S. Pat. No. 3,149,861 to Larson issued Sept. 22, 1964. As theredescribed, a sleeve is compressively reduced, such as by crimping, ontoa pipe end to provide the required interconnection between the sleeveand the pipe end.

There are many easy recognized advantages to the concept. Pipe joiningcan be accomplished without the need for welding or heat. Minimum pipeend preparation is required, and, the joint, once made, is permanent andnot easily subject to tampering. However, in the practice of thetechnology many problems have arisen which have limited its applicationto small diameter pipes or tubes, and, as a result, its popularity hasbeen restricted.

One significant impediment to more widespread adaptability is thelimited resistance of such pipe joints to axial forces which occur uponpressurization of the pipeline incorporating the joint. Another problemis that the joint has little resistance to torsional loading.

Recognizing these problems, Mannesmann A. G. has over many yearsdeveloped significant improvements in such joints. These have includedmodifications in the configuration of the crimped pattern as well asimproved sealing means. These improvements have significantly enhancedthe adaptability and market acceptance of crimped sleeve to tube pipejoints, sometimes referred to as the "press fitting system". As aresult, its popularity has grown substantially.

Despite this, press fitting systems in current usage are limited tosmall diameter tubing, and, such systems are unable to satisfy the needsof users of relatively larger diameter tube. In those instances, theproblems of inadequate axial and torsional resistance persisted.

In apparent recognition of these problems, it has been suggested inJapanese patent 88939 issued May 7, 1980 in the name of Nippon BenkanKogyo K.K. that further modifications be made, particularly in the shapeof the crimp. Other suggestions which would result in an increase inresistance to axial and torsional loading are made which incorporate ahexagonal crimp in the sleeve and the pipe, the hexagonal crimp beingeffective not only to resist axial separation of the sleeve and pipe,but also being effective to resist torsional loads that may be imposedon the joint. It is believed that the product described in the Japanesepatent has not been marketed. Further, as hereinafter more fully set outin the Japanese patent, the configuration there described does notadequately solve the problem of providing sufficient resistance toseparation of the sleeve from the tube.

When pressurized, internal pressure in the pipe acts to produce forcesin an axial direction to cause separation of the sleeve from the pipeend. Pressure within the pipe also acts in radial directions to expandthe crimped joint back to its in-round condition, which can result inrelease of the sleeve from the pipe end.

These conditions act in unison and if sufficient to cause a weakening ofthe joint the results can be quite serious, particularly if thepressurized fluid being conveyed is flammable, toxic, corrosive oracidic, or, is heated fluid, such as found in a domestic or industrialheating system.

As aforementioned, the formation of sleeve to tube joints generallyinvolves the positioning of a sleeve over the pipe end. The sleeveincludes a circumferential channel on its inner surface in which asealing member, preferably an seal ring is received. The internaldiameter of the sleeve and that of the seal ring must be sufficientlylarge to permit insertion of the sleeve and its contained seal ring ontothe pipe end without cutting or abrading the seal ring, and, in theabsence of an interference fit of the inner circumference of the sleevewith the exterior surface of the pipe.

As a result the inner circumferential length of the sleeve is greaterthan the outer circumferential length of the pipe. This inhibitscontinuous face to face seating of the sleeve onto the pipe during thecrimping operation, unless some manner of shrinking the internaldiameter of the sleeve can be devised. However, shrinking of thediameter of the sleeve poses unusual problems, in that the assembly ofthe joint will ordinarily take place at the actual site of theinstallation, and often times in locations that are not readilyaccessible and which require effecting the crimp in the joint from onelateral side of the joint.

Special crimping tools have been devised to accomplish this purpose, asuitable one being sold by Novopress GmBH & Co. KG. Thus, presently usedcrimping tools incorporate a pair of jaws that move towards the outerperiphery of the sleeve, and effect the interconnecting crimp betweenthe sleeve and the pipe. This movement of the jaws, however, results indisplacement of the sleeve to an out of round condition relative to thepipe, and most importantly, results in uneven stressing of the sealring. The body of the seal ring can move or displace circumferentiallyof the pipe from the location of first engagement of the crimping jawsto the position of terminal engagement of the crimping jaws.

This can result in uneven stressing of the seal ring, and isparticularly disadvantageous where larger diameter sleeves and pipelineare to be used because it contributes to failure of the joint underpressure loading. Additionally, it severely limits the maximum internalpressure to which the piping system can be subjected without failure ofthe seal provided by the seal ring.

The present practice of employing a crimp having an hexagonal formsimulating the exterior surfaces of a threaded nut does not overcome theproblems. The pressure within the piping system acts radially outwardlyon the flats of the hexagon, which have a low resistance to outwardbowing, and, can cause outward ballooning of the flats, with aconsequential decrease in the holding power of the joint, and subsequentfailure of the joint.

The formation of a hexagonal crimp encircling the joint does have someadvantage in that it increases resistance of the joint to torqueloading. However, this is of only limited effect, in that the hexagonalcrimped outer surface of the pipe has edges that can act as cammingmembers operative to force the hexagonal crimp in the sleeve towards anin-round condition. If this should happen, the resistance of the jointto failure under pressure loading is seriously impaired.

SUMMARY OF THE INVENTION

The present invention is directed to overcoming these problems in knowncrimped sleeve to tube joints, in order to provide a crimped sleeve totube joint that can withstand pressures considerably in excess of thoseconsidered to be an upper limit, and which can be used in conjunctionwith pipes of larger diameters and tolerances than those contemplatedaccording to the prior art teachings, and additionally, which permitscrimped sleeve to tube joints to be employed for the interconnection ofthin walled pipe of a diameter considerably in excess of the one inchpipe of the prior art.

The present invention provides crimped sleeve to tube joints that can besuccessfully employed in piping systems in which the internal pressureexceeds 1.000 pounds per square inch, and, the pipe diameters exceed 2inches.

This is accomplished according to the present invention by severalmodifications of the prior art teachings in order to arrive at a crimpedsleeve to tube joint of considerably enhanced strength, and which is farless prone to leakage of the formed joint.

Essential to the inventive concept is the greater equalization of thestresses produced in the seal ring during the crimping operation.

Preferably, crimping of the flange of the sleeve containing the sealring is commenced prior to crimping of the sleeve to the pipe end, toconfine and stress the seal ring prior to axial immobilization of thesleeve relative to the pipe, thus allowing for limited axial movementbetween the sleeve and the pipe during the crimping of the sleeveflange.

Crimping of the sleeve to the pipe then continues in a manner producingdiametrically opposed arcuate channels in the sleeve and in the pipe,the respective arcuate channels being separated one from the other by anaxially straight un-crimped portion of the sleeve and pipe. The axiallystraight un-crimped portions of the sleeve and pipe then act as strutsinterconnecting the portions of the sleeve and of the pipe on oppositeaxial sides of the crimp. The struts are themselves highly resistive toaxial elongation of the sleeve or of the pipe, and are operative topreserve the structural integrity of the formed crimp.

The arcuate crimps extend inwardly of the pipe diameter, and, duringtheir formation produce compressive stresses in the struts, which areeffective to resist such compressive stresses, thus enabling formationof the crimp in a precise and dimensionally accurate manner.

The crimps themselves are formed as surfaces arranged in crenelateformation that converge towards the longitudinal axis of the pipe.

Crimping of the sleeve and tube in the presence of the struts results ina localized shrinkage in the internal diameter of the sleeve, which isoperative to take up the clearance between the internal circumference ofthe sleeve and the external circumference of the pipe end.

By inwardly crimping the joint in this manner, a very significantadvantage is produced in the strength of the crimped joint. When thejoint is subjected to pressure internally of the pipe, then, the flanksof the crimps are placed under compressive stresses and attempt toexpand radially outwardly to the initial in-round condition of thesleeve and pipe.

Such expansion is, however, inhibited by the axially adjacent in-roundportions of the sleeve, sides of the crimp and pipe, which are thenplaced under a hoop stress. For the crimps to move back to theirin-round condition, axial elongation of the sleeve and pipe at thelocation of the crimps would be required. However, such axial elongationis inhibited by tensional stress produced in struts at the respectiveends of the crimps.

The inability of the struts to elongate negates any opportunity for thesleeve and pipe to elongate axially at the location of the crimps, andin turn, negates opportunity of the crimps to return to an in-roundcondition of the sleeve and pipe throughout the arcuate extent of thecrimps, such as could occur in the event that the crimps were to beformed as continuous crimped grooves completely encircling the sleeveand the pipe. In such a construction of completely encircling crimps,then, the pipe and sleeve would act in the manner of a bellows, thuspermitting axial elongation of the sleeve and the pipe and a substantialreduction in the strength of the joint under the axial loading generatedby the pressure internally of the pipe.

In this manner, a crimped sleeve to tube joint is provided of veryconsiderably enhanced resistance to failure under axial loading producedby pressurization of the system. Also, a joint is provided in which theefficacy of the sealing power of the seal ring is greatly enhanced, thusenabling operation of a large diameter piping system incorporating thejoint of the invention at pressures considerably higher than previouslyconsidered to be the upper limit.

Resistance to torsional loading of the joint is enhanced by the strutsin the same manner as the resistance to axial loading of the joint isenhanced by the struts. The struts lie on diameters greater than theinner diameter of the crimps, thus inhibiting relative rotation betweenthe sleeve and pipe.

These desirable attributes can be accomplished by the use of relativelysimple power tools that are readily portable and which can be used withease in actual on-site locations, thus eliminating the necessity ofpre-assembly under factory conditions.

DESCRIPTION OF THE DRAWINGS

The prior art construction and preferred embodiments of the inventionare now described with reference to the accompanying drawings, in whichFIGS. 1 through 4A are illustrative of the prior art, and, FIG. 5through 12 are illustrative of the present invention, and, in which:

FIG. 1 is a longitudinal cross-section through a prior art sleeve totube joint;

FIG. 2 is a cross-section of FIG. 1, and additionally showing formingdies used in the formation of the joint;

FIG. 3 is a diagrammatic illustration of the prior art manner ofcrimping;

FIG. 4 is a diagram illustrating stress distribution in the seal ringemployed in prior art FIG. 1, and

FIG. 4A is a diagram illustrating the effects of torsional and radialexpansion forces exerted on a hexagonal crimp of prior art FIG. 1;

FIG. 5 is longitudinal cross-section through a tube and sleeve, prior tocrimping according to the present invention;

FIG. 6 is a front view of crimping dies employed in the crimpingoperation of the present invention;

FIG. 7 is a top view of the bottom die shown in FIG. 6;

FIG. 8 is a longitudinal cross-section through a sleeve to pipe jointaccording to the present invention;

FIG. 9 is a transverse cross-section taken on the line 9--9 of FIG. 8;

FIG. 10 is a longitudinal or axial cross-section through a crimping dieas used in the present invention, and illustrates the successive stepsof formation of the sleeve during a crimping operation;

FIG. 11 is illustrative of the stress distribution in the seal ringresulting from the teachings of this invention; and,

FIG. 12 is a longitudinal cross-section through a crimp as formedaccording to the present invention.

DESCRIPTION OF THE PRIOR ART

The sleeve to tube joint now discussed with reference to FIGS. 1 through4A of the drawings is exemplary of a sleeve to tube joint constructionas previously known in the art. In FIGS. 1 and 2, the tube is indicatedat 10 and the sleeve at 12, the joint being shown in the process ofassembly by means of the use of dies 14 and 16 that are moved arcuatelyrelative to each other to effect compressive shrinkage of a curvedannular flange 18 in which an seal ring is confined.

The jaws 14 and 16, respectively, include forming lands 22 and 24 attheir opposite axial sides, which are respectively formed as one half ofa hexagon in peripheral contour. Upon closing of the dies, the annularflange 18 is compressed radially to reduce the diameter of the flange,and simultaneously, the tube and sleeve are compressively crimped intoan hexagonal form.

The compression of the flange 18 results in biting of the free edge ofthe flange into the exterior of the tube 10, and additionally, providesthe hexagonal crimp. This substantially increases the resistance of thejoint to separation under axial loading, and, significantly increasesthe resistance of the joint to oppositely acting torsional loads exertedon the tube 10 and sleeve 12.

However, the formed joint, while being of increased strength, is limitedin its application to relatively low-pressure piping systems, and, onesin which torsional loading between the sleeve and the tube is notanticipated, or, is expected to be of a minor order.

The limitations imposed on the pressure loading, and also the diameterof such a joint as formed according to the prior art, are a consequenceof the manner in which the annular flange 18 is compressively shrunk,and, as a consequence of the employment of a hexagonal crimp, as nowdiscussed with reference to FIGS. 3, 4 and 4A.

Tools as presently available for effecting the crimp include dies thatmove along arcuate paths as the dies move towards face engagement.

The effects of such a movement are illustrated in FIG. 3, in which thedies 14 and 16 are shown as moving along arcuate paths as indicated bythe arrows A--A.

Such a movement of the dies results in the dies initially engaging thesleeve 12 at positions B--B, displaced to one side of the longitudinalaxis of the sleeve, formation of the joint commencing at the pointsB--B. This, however, results in distortion of the sleeve, and ultimatelydistortion of the tube into an out-of-round condition, which ultimatelyresults in uneven stressing of the seal ring, and which can lead tofailure of the seal provided by the seal ring under pressure loading.

As is illustrated in FIG. 4A, commencement of formation of the jointresults in a compressive stress being applied to the seal ring over thearcuate extent of the sleeve subtended by the angle B1. Such a radiallyinward compressive stress is not accompanied to any material extent bycircumferential compression in the direction of the arrows C, the sealring at that time being under zero circumferential compression, andbeing capable of movement circumferentially of the sleeve and tube in amanner permitting the dissipation of such circumferentially actingcompressive stresses.

As the dies progressively move along their arcuate paths,circumferentially acting compressive forces are generated in the sealring, which result in displacement of the seal ring circumferentiallywithin the flange of the sleeve to that side of the sleeve opposite tothe points B--B of initial engagement with the dies.

This can result in over-compression of the seal ring at one side of thejoint as indicated by the plus signs, with a possibility of extrusion ofthe material of the seal ring prior to completion of formation of thejoint. This can result in zones which are under little or nocircumferential compression as indicated by the zero signs, and furtherzones in which the compressive stresses are exclusively radial, to theelimination of any circumferential compressive stresses, as indicated bythe minus signs.

Optimally, the compressive stresses produced in the seal ring should beequal at all positions circumferentially of the seal ring in order toprovide for maximum sealing efficiency of the seal ring. However, such acondition is only possible in the event that an infinite number of dieseach moving radially inwardly of the axis of the sleeve and tube areprovided, which clearly, is impractical in actual practice, other than,for example, by a hydro-forming operation, which clearly is impracticalother than in a workshop.

The strength of such a prior art joint, however, is dependent on themanner in which the sleeve has been crimped directly to the tubeexterior. The biting engagement of the sleeve flange with the tubeexterior has relatively poor resistance to axial loading of the joint,such as could cause the sleeve to pull off the end of the tube, and hasrelatively poor resistance to oppositely acting torsional forces thatcould cause rotation of the sleeve relative to the tube and release ofthe crimped interconnection.

While providing a joint of enhanced strength, the strength of a jointprovided by a hexagonal crimp and is encumbered with limitations, as nowdiscussed with reference to FIG. 4A.

FIG. 4A illustrates schematically the effects of pressure on theinterior of a sleeve or tube having an hexagonal crimp, and is adiagrammatic cross-section through such a crimp.

Up to relatively low internal pressures, the walls of the hexagon willexhibit little or no movement. However, upon a rise in internalpressure, then, a point is reached at which the respective planar wallscomprising the hexagon will commence to bow radially outwardly in thedirection of the arrows D, i.e., the hexagon will attempt to revert toits original truly circular shape.

Concurrently with this outward bowing movement of the planar walls ofthe hexagon, a hinging movement will occur at the junctures E ofadjacent pairs of the planar walls, which will attempt to move in thedirections of the arrows F, this resulting in an inward hinging movementat the corners of the hexagon in the direction of the arrow G, thisfurther allowing the hexagonal shape to return to its original circularshape.

If the hexagonal configuration of the tube proceeds into round, thiswill cause a corresponding movement of the hexagonal crimp in thesleeve, which also will move into round. If the respective hexagonalcrimps move into round, then, the securement against axial displacementof the sleeve and tube relative to each other is lost.

Such expansion of forces of the hexagon into round can be occurring inthe presence of torsional forces acting oppositely on the sleeve and onthe tube. If this condition occurs, then, the corners of the hexagonimpressed in the tube and will act as camming members acting to cam theplanar surfaces of the hexagon in the sleeve radially outwardly, again,acting to displace the planar surfaces of the hexagon back to theoriginal circular form. If this should happen, then, resistance totorsional loading of the crimp will drop to an entirely negligibleamount. Further, one of these conditions can aggravate the other, i.e.,escalating pressure within the tube will reduce the torque absorbingcapabilities of the crimp, and, excessive torque applied to the crimpwill reduce the capability of the joint to withstand pressures of apredetermined maximum.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 5 through 11, a preferred embodiment of thepresent invention is disclosed, by means of which a sleeve to tube jointof increased resistance to axial separation and increased resistance totorsional loading is provided.

Referring now to FIG. 5, the tube previously identified is indicated at10, the sleeve is indicated at 12, and, the annular flange of the sleeveis indicated at 18.

The internal diameter 30 of the sleeve 12 is slightly greater than theouter diameter 32 of the tube 10, in order to provide a clearance offrom 1.2 millimeters to 1.5 millimeters, such that the sleeve can beslid onto the pipe in the absence of an interference fit between thosemembers.

The tube and the sleeve are each circular in transverse cross-sectionabout a central axis 36 common to both the tube and the sleeve.

The end of the sleeve remote from the annular flange 18 is stepped at38, thus limiting the extent to which the sleeve can be moved axially ofthe tube.

The annular flange 18 at the free end of the sleeve is comprised of aradial flange 40 which continues at its outer periphery into an arcuateportion 42, the arcuate portion 42 continuing tangentially into aninclined portion 44 defining an angle of between 37° and 53° relative tothe central axis 36, to provide a cone angle of between 74° and 106°.

Positioned within the annular flange 18 is an seal ring 46, the sealring 46 being of a cross-sectional diameter that is related to theinternal diameter of the sleeve 12 on a 1:10 ratio. The inner radius ofthe arcuate portion 42 is the same as the cross-sectional radius of theseal ring 46, such that the arcuate portion 42 closely embraces theouter surface of the seal ring 46 through an angle of between 127° and143°, depending on the selected cone angle. The seal ring 46 is ofsufficient rigidity that it will remain in-situ within the arcuateportion 42, once installed therein for the sleeve and the seal ring tobe handled as a unitary sub-assembly.

The inner diameter of the seal ring 48, and, the inner diameter of theradial flange 40 each is slightly greater than the inner diameter 30 ofthe sleeve 12, this being in order to avoid damage by scuffing of theinner diameter of the seal ring 46 as the sleeve 12 is passed onto thepipe, and also, in order to allow for the required extent of compressivereduction of the flange 18 during the crimping operation before theinner diameter of the radial flange 40 engages and bites into the outersurface of the tube 10.

Reference is now made to FIGS. 6 and 7 of the drawings, which illustratethe dies employed in the crimping operation.

In FIG. 6 and 7, the respective upper and lower dies 14 and 16 eachinclude five die sections, as is more clearly illustrated in FIG. 7.These five die sections comprise axially outer sleeve crimping sections52 and 54, intermediate flange forming sections 56 and 58, and, acentral flange forming section 60. While these sections are duplicatedsymmetrically on each axial side of the central flange portion 60, itwill be apparent that only three of the sections will be employed ineffecting a crimp, either the sections 52, 56 and 60, or the sections54, 58 and 60. The reason for providing duplicate sections in mirrorimage is in order to allow the die to be employed in effecting either acrimp to the right hand end of a sleeve, or the left hand end thereof.

The transverse section of the dies 14 and 16, as taken in the X-Y planeis discussed later with reference to FIG. 10. FIG. 6 shows a front viewof the dies as seen from either side in the X-Y plane, the respectivedies 14 and 16 being identical with each other and symmetrical in allrespects.

The respective dies 14 and 16 are moveable away from each other in thedirection of the Y axis to permit insertion of an unformed annularflange 18 (not shown in FIG. 6) into the jaws of the dies, and are thenmoveable towards each other in the direction of the Y axis for them toeffect crimping and compressive reduction of the sleeve and the annularflange.

A selected one of the crimping sections 52 and 54 is employed forcrimping the sleeve. Each of those sections includes an arcuate portion62 which has its radius 64 generated from a point Z1 or Z2 on the Y axisthat is spaced from the X-Z plane, such that the radius 64 is less thana radius taken from the Z axis. The arcuate extent of the respectiveportions 62 is 65° symmetrically on each side of the Y axis for a totalof 130°, the arcuate portion 62 being of fixed radius throughout thisarcuate extent.

The remaining extent of the crimping sections 52 or 54 are comprised oftangents to the arcuate portions 62, which diverge radially outwardly ofthe Y axis through an angular extent of 25°, and which terminate at theend of faces of the dies 14 and 16 in axial alignment with the edges ofthe intermediate flange forming sections 56.

The intermediate flange forming sections 56 and 58 and the centralflange forming section 60, while appearing circular in FIG. 6, are notin fact truly circular, but are in fact radii taken from the Z1 or theZ2 axes, throughout an arcuate extent of 180°, the respective arcuateportions then proceeding into transitional portions for the distanceZ1-Z or Z2-Z.

The reasons for this configuration of the dies is now explained.

On closure of the dies, the leading portions of the central flangeforming section 60 and one of the intermediate flange forming sections56 and 58 will engage the annular flange 18 at diametrically oppositesides thereof, and, will act to force the annular flange radiallyinwardly at the points of engagement and into compressive engagementwith the outer surface of the tube at that location.

In so doing, both the annular flange and the tube will be forced into anelliptical condition, with the minor axis of the ellipse lying on the Xaxis and the major axis of the ellipse lying on the Y axis.

Continued movement of the dies 14 and 16 towards each other will thencause compression of the annular flange, which has increased in radiusalong the Y--Y axis, the compression commencing at the Y--Y axis, whichattempts to return the annular flange to an in-round condition.

As this occurs, the annular flange attempts to form dual ellipses havingtheir major axes displaced 90° one from the other. Continued compressionthen results in the formation of further major axes displaced at 45°relative to each other, followed by the development of further majoraxes at 22.5° to each other, followed by further major axes oriented at11.25° relative to each other and so on, until such time as the entireperiphery of the annular flange 18 is placed under a compressive hoopstress, at which time compressive reduction of the diameter of theflange proceeds.

In this manner, a progressively escalating number of axes passingthrough the Z--Z axis are developed as the dies move towards each other,this resulting in the development of a compressive stress in thecontained seal ring in an entirely symmetrical manner which isineffective to produce circumferential displacement of the seal ring.

Of essence to this concept is the initial reduction in radius of theannular flange along the X axis to produce elongation of the radius ofthe flange along the Y axis such that the annular flange initiallyassumes an elliptical configuration, and is then progressively returnedto a circular configuration during the compressive reduction of theflange. Crimping of the flange 18 in this manner results in a verysubstantial equalization in the circumferential compressive stressesinduced in the seal ring 20, as is diagrammatically illustrated in FIG.11, in which the plus signs indicate the initial zones ofcircumferential compression, and the double plus signs indicate zones offinal circumferential compression.

As will be explained later with respect to FIG. 10, this compressivereduction commences prior to the crimping operation, at which time thesleeve is free to move axially of the tube, and is available toaccommodate the compressive reduction of the conical flange portion ofthe sleeve in the absence of axial elongation of the sleeve.

FIGS. 8 and 9 illustrate a finished joint according to the presentinvention, respectively in longitudinal cross-section, and, intransverse cross-section in a plane which includes the sleeve to tubecrimp. As will be seen, the dies 14 and 16 in moving towards each otheralong the Y axis, are operative firstly to effect compressive reductionof the annular flange 18 to place the seal ring 20 under radial andcircumferential compression, displacement of the material of the sealring being dominantly in an axial direction relative to the tube, andinto the free zone existing in the sleeve in the interior of the annularflange 18.

In moving towards the sleeve 12, the dies 14 and 16 commence compressivedeformation of the annular flange 18, and then, as more particularlydescribed with respect to FIG. 10, they then commence compressivedeformation of the inclined flange portion 44, this being prior to thecommencement of crimping of the sleeve 12 to the tube 10. Thus, thesleeve 12 is at that time free to move to a limited extent in directionsaxially of the tube 10, thus relieving the inclined flanged portion 44from stresses acting axially of the sleeve, and which would act toresist deformation of the inclined flange portion 44.

Subsequent to the commencement of crimping of the inclined flangeportion 44, then, the opposite pair of the sleeve crimping sections 54engage the exterior of the sleeve 12, and progressively formdiametrically opposed, circumferentially arcuate crimps 68, 68 in thesleeve 12 and tube 10. The crimps 68 do not merge into each other attheir respective opposite ends, but instead, by virtue of theconfiguration of the crimping sections 54 leave intact an axiallystraight uncrimped struts 70 connecting the sleeve and tube on one axialside of the crimps with the sleeve and tube on the opposite axial sideof the crimps. The struts 70 inhibit elongation of the sleeve and tubein the vicinity of the crimps 68, and serve to maintain the structuralintegrity of the crimps 68 under pressure loading internally of the tube10, and, in the presence of torsional forces acting between the sleeve12 and the tube 10.

Referring now to FIG. 10, a cross-section through the die 14 is shown inenlarged detail, the cross-section being taken in the Y-Z plane asrelated to FIG. 7. In FIG. 10, for clarity of illustration, the radialflange 40, the arcuate portion 42 and the inclined portion 44 of theannular flange 18 have been illustrated diagrammatically as a singleline. Also, for clarity of illustration, the seal ring 20 and the tube10 have been omitted.

On movement of the die 14 in the direction of the arrow H, the initialengagement of the die with the sleeve 12 is by the axially oppositeshoulders 72 of the die which provide a transition between the centralflange forming section and the intermediate flange forming sections 56and 58. The engagement of the shoulders 72 with the annular flange 18will cause the radial flange 40 to displace axially towards the position40', and also will cause deformation of the inclined portion 44 in aradial direction towards the location 44'.

Radially inward deformation of the inclined flange portion 44, will inturn cause the sleeve 12 to move axially towards the radial flange 40,such axial movement of the sleeve 12 being possible until such time asthe crimping section 52 engages the sleeve 12 with sufficient force toinhibit further such axial movement of the sleeve 12 to the position12'.

By allowing axial movement of the sleeve 12, the inclined flange portion44 is relieved from tensile stresses acting in the direction of the tubeaxis, and thus, is more readily deformed in the absence of tensilestresses produced in the inclined flange portion 44, such as would arisein the event that the sleeve 12 was incapable of axial movement to theposition 12'. The result is that the tensile forces induced in theinclined flange portion 44 are substantially reduced, thus substantiallyreducing the tendency of the inclined flange portion 44 to spring backtowards its original position in an attempt to relieve tensile stressesstored in the inclined flange portion 44, and in turn acting to maintaincompressive stresses existing in the inclined flange portion 44.

At the same time as axial movement of the radial flange 40 and theradially inward deformation of the inclined flange portion 44 commences,the arcuate portion 42 of the annular flange 18 bows upwardly towardsthe position 42', in this manner reducing the radius of the arcuateportion 42, and acting to place the contained seal ring undercompressive stresses to further retain the seal ring againstdisplacement within the annular flange 18.

This upward bowing movement in combination with the radially inwarddeformation of the flange portion 44, will cause the arcuate portion 42to rotate about its point of radial generation in a clockwise direction,and will in turn move the radial flange 40 into a position 40" in whichit extends forwardly of the sleeve 12 at an equal but opposite angle tothe finally formed flange portion 44, as indicated in FIG. 8.

Downward movement of the die 14 continues, until such time as the radialflange 40 has reached the position 40" and the inclined flange portion44 has reached the position 44", the arcuate portion 42 at that timehaving reached the inner surface of the central flange forming section60, subsequent to which compressive reduction of the annular flange 18commences as the die 14 continues its downward movement.

During the latter part of the downward movement of the die 14, thesleeve crimping section 52 contacts the sleeve 12, the crimping of thesleeve 12 to the tube 10 then commencing and continuing as the die 14moves to its final position. At this point, the radial flange 40 willhave become firmly embedded in the exterior of the tube surface byvirtue of the compressive reduction of the annular flange 18, tensilestresses have been relieved in the inclined flange portion 44, and,commencement of the crimp in the sleeve 12 will have occurred subsequentto the relief of tensile stresses in the inclined flange portion 44.Thus, upon removal of the die 14, the compressively reduced annularflange is located axially of the pipe 10 at the inner periphery of theradial flange 40, and, at the position of the crimp, this reducing anytendency of the sleeve 12 to move reversely along the tube as aconsequence of spring forces stored in the inclined flange portion 44and consequential reduction in the compressive stress applied to thecontained seal ring.

By arranging for the flange portions 40 and 44 to move to substantiallyequal and opposite angles, equalization of the compressive stressesproduced in the seal ring 20 is further enhanced, and, enhanced seatingof the seal ring on the pipe 10 is produced.

From the previous discussion of the dies employed for performing thecrimping operation, it will be apparent that what might be referred toas banana shaped crimps are formed in the sleeve and the pipe atpositions spaced circumferentially of the pipe, the respective bananashaped crimps being isolated one from the other by the axially straightportions 70 providing the struts. The advantages resulting from thisconstruction will now be described with reference to FIG. 12.

Referring now to FIG. 12, it will be seen that the crimps 68 each are ofU-shaped cross-section in the direction of the axis of the pipe 10. Thefact that the crimp protrudes radially inwardly of the tube 10 is ofminor consequence, in that high velocity flows of fluids containedwithin the tube 10 is not contemplated.

The U-shaped crimps are produced by the sleeve crimping sections 52 and54 of the dies 14 and 16.

The crimp thus produced comprises oppositely inclined walls 110 formedin the tube 10, and oppositely inclined walls 112 formed in the sleeve12, the respectively oppositely inclined walls 110 and 112 beinginterconnected with each other through an axially short transitionalcylindrical portion 114.

Radially inward movement of the material of the sleeve 12 during thecrimping operation, will be effective to shrink the diameter of thesleeve 12, thus ensuring intimate face to face contact between the outersurface of the tube 10 and the inner surface of the tube 12 toimmobilize the sleeve 12 relative to the tube 10.

If now fluid under pressure is introduced into the tube 10, then, thatfluid under pressure will act both in axial and radial directions, and,in the event that the internal pressure is sufficient, will attempt toreturn the crimp to the original in-round condition of the tube 10 andthe sleeve 12.

Radially acting forces will result in compressive stresses beingdeveloped in the oppositely inclined wall portions 110, 112 of thecrimp. Those wall portions are highly resistive to the return of thecrimp to its original in-round conditions, unless elongation of thecrimp in an axial direction also occurs. Such elongation is prevented bythe struts 70.

For example, radially outward forces K acting on the interior of thecrimp will result in compressive forces L in the side walls of thecrimp, which act as buttresses, the compressive forces L beingdissipated in the immediately axially adjacent portions of the tube andsleeve as stresses acting to expand the unformed portions of the tube 10and sleeve 12. The adjacent sections of the tube 10 and sleeve are,however, incapable of expansion to any material extent in that they arealready in an in-round condition, the adjacent portions of the tube 10and sleeve 12 thus being available to provide the necessary reactionforces M counterbalancing the radially outwardly acting forces L, i.e.,a system of balancing forces is produced that will inhibit the expansionof the crimp in radially outward directions back to the in-round initialcondition of the tube 10 and sleeve 12.

Such an expansion readily would occur in the presence of axial andradial forces produced within the pipe 10 in the event that the crimps68 were to extend continuously around the tube 10 and sleeve 12. In suchan event, then, the crimps would act as a bellows permitting axialmovement of the adjacent portions of the tube 10 and sleeve 12 inopposite axial directions, at which time the radially outward forcesacting on the crimp would be operative to return the crimp to itsinitial in-round condition.

Any such movements of the crimp are inhibited by the struts 70, which atthat time are placed in tension, and, which are operative to inhibit anysuch axial movement of the sections of the tube 10 and pipe 12 onopposite sides of the crimps 68.

Additionally, as the crimp is held against radially outward expansion bythe struts 70 and is incapable of returning back to its in-roundcondition, the cross-section of the tube 10 and pipe 12 in the locationof the crimps 68 is non-circular, thus inhibiting relative rotationbetween the tube 10 and the sleeve 12 on the application of torsionalforces to those members.

As will be apparent from the preceding discussion, the specific form ofcrimp according to the present invention is a major factor enablingsleeve to tube joints to be produced that can withstand considerablyhigher internal pressure than known crimped sleeve to tube joints, thecrimp of the present invention, together with the manner ofcompressively reducing the annular flange containing the seal ring andthe equalization of circumferential stresses in the seal ring eachacting synergism to provide a crimped seal to tube joint that canwithstand internal pressures greatly in excess of internal pressuresconsidered maximum in the prior art, and which also enables satisfactorycrimped sleeve to tube joints to be produced in pipes of far greaterdiameter than those previously contemplated, thus very considerablyenhancing he utility of such sleeve to tube joints.

While a sleeve to tube joint has been described employing twodiametrically opposite crimps with two diametrically struts, theinvention is not restricted to the use of two diametrically oppositecrimps. Any number of individual crimps and a corresponding number ofstruts can be employed, for example, four such crimps arranged indiametrically opposite pairs and four such struts arranged diametricallyopposite pairs. Such a construction would have increased resistance toangulation of the axis of the pipe and sleeve at the crimp, whileretaining all of the advantages of the present invention.

While the crimps have been described as being of U-shaped formation, theinvention is not limited to such a U-formation. The crimps may be ofother shapes producing a concave crimp surface on the outer side of thesleeve and a convex crimp surface on the inner face of the pipe whichare capable of producing compressive forces within the walls of thecrimp on the pressurization of the pipe interior, such as a V-shapedcrimp formation.

We claim:
 1. A crimped sleeve to the tube joint, including:a tube ofcircular transverse cross-section; a sleeve of circular transversecross-section telescoped over said tube; a seal ring containing flangeat one end of said sleeve; a seal ring contained within said seal ringcontaining flange; said seal ring containing flange having beencompressively reduced into engagement with the outer circumference ofsaid tube, and said sleeve and said tube having been crimped at alocation spaced from said one end to immobilize said sleeve againstaxial and circumferential movement relative to said tube, furtherincluding: at least two crimps extending inwardly of the outer peripheryof said respective sleeve and tube, and each extending arcuately of thecircumference of said respective sleeve and tube on a constant radius ofsaid respective sleeve and tube taken from the longitudinal axis of saidsleeve and tube, said respective crimps being separated from each othercircumferentially of said sleeve and tube by struts provided by axiallyextending portions of said sleeve and tube extending axially along theoriginal radius of said respective sleeve and tube at the radiallyoutermost portions of said sleeve and tube, said crimps each beingconcave inwardly of the outer surface of said respective sleeve andtube; said respective crimps each including radially outwardly divergentportions at the respective opposite ends of said circumferentiallyextending crimps; said crimps, when viewed in transverse cross-sectiontaken in a plane which includes the longitudinal axis of said respectivesleeve and tube, extending symmetrically to opposite sides of a planetransverse to the longitudinal axis of said respective sleeve and tube,and each including radially inwardly convergent side faces providingtransitions between the outer circumference of said respective sleeveand tube and a radially inner portion of said respective crimps; saidrespective inwardly convergent side faces each extending on the surfaceof an imaginary cone having its perpendicular axis coincident with thelongitudinal axis of said respective sleeve and tube.
 2. The crimpedsleeve to tube joint of claim 1, in which said crimps each include anarcuate portion extending at a fixed radius from the longitudinal axisof said respective sleeve and tube, each said arcuate portionterminating in a straight portion which extends tangential to saidarcuate portion and which terminates at the outer circumference of saidrespective sleeve and tube at said axially extending struts.
 3. Thecrimped sleeve to tube joint of claim 1, including two said crimpsarranged diametrically opposite each other to provide a crimp formationof lemon shape when viewed in transverse cross-section in a planetransverse to the longitudinal axis of said respective sleeve and tube.4. The crimped sleeve to tube joint of claim 1, in which said axiallyextending struts, when viewed in cross-section in a plane transverse tothe longitudinal axis of said respective sleeve and tube, each arespaced from the longitudinal axis of said respective sleeve and tube bya distance which is the same as the radius of the associated said sleeveand tube when taken at positions spaced from said crimps and transverseplane.
 5. The crimped sleeve to tube joint of claim 1, further includingaxially extending portions of said crimps providing a transition betweensaid radially inwardly extending portions of said crimps.
 6. The crimpedsleeve to tube joint of claim 1, including plural said at least twocrimps arranged in spaced relation axially of the longitudinal axis ofsaid respective sleeve and tube.
 7. The crimped sleeve to tube joint ofclaim 1, in which said crimps are of greater length circumferentially ofsaid sleeve and tube than is the width of said struts circumferentiallyof said sleeve and tube.
 8. The crimped sleeve to tube joint of claim 1,in which said crimps are substantially of U-shaped cross-section andinclude side walls extending in planes inclined relative to each otherand converging inwardly towards the longitudinal axis of said respectivesleeve and tube.
 9. The crimped sleeve to tube joint of claim 1, inwhich said crimps include radially outwardly divergent walls extendingradially inwardly toward the longitudinal axis of said respective sleeveand tube.
 10. The crimped sleeve to tube joint of claim 1, in which saidseal ring containing flange includes a radial annular flange engaged atits inner periphery with the outer periphery of said tube, and in whichsaid flange and said crimp are operative to maintain said flange and thecontained seal ring in a compressively stressed condition.
 11. Thecrimped sleeve to tube joint of claim 1, wherein said seal containingflange comprises:flange means including a first annular portion of saidsleeve integral with an axially extending portion of said sleeve, asecond annular portion of said sleeve providing an end of said sleeve,and a radially outwardly extending convex portion of said sleeveproviding a transition between radially outer portions of said first andsecond annular portions; said respective first and second annularportions diverging radially inwardly from said convex portion at equaland opposite angles on opposite sides of a plane transverse to thelongitudinal axis of said respective sleeve and tube; and said seal ringcomprises, an elastomeric seal ring compressively contained within saidflange portion and in continuous surface contact with the inner surfaceof said flange means; an inner radius of said radially outwardly convexportion being of a radius which is 90% of the initial cross-sectionalradius of said radially outer convex portion prior to crimping.
 12. Thecrimped sleeve to tube joint of claim 11, in which said crimp means isspaced axially of said flange means by a distance in excess of theinitial cross-sectional radius of said radially outer convex portion.13. A crimped sleeve to tube joint, including:a tube of circulartransverse cross-section; a sleeve of circular transverse cross-sectiontelescoped over said tube; a seal ring containing flange at one end ofsaid sleeve; a seal ring contained within said seal ring containingflange. said seal ring containing flange having been compressivelyreduced into engagement with the outer circumference of said tube, andsaid sleeve and said tube having been crimped at a location spaced fromsaid one end to immobilize said sleeve against axial and circumferentialmovement relative to said tube, further including: two crimps extendinginwardly of the outer periphery of said respective sleeve and tube, andeach extending arcuately of the circumference of said respective sleeveand tube on a constant radius of said respective sleeve and tube takenfrom the longitudinal axis of said sleeve and tube, said respectivecrimps being separated from each other circumferentially of said sleeveand tube by struts provided by axially extending portions of said sleeveand tube extending axially along the original radius of said respectivesleeve and tube, at the radially outermost portions of said sleeve andtube, said crimps each being concave inwardly of the outer surface ofsaid respective sleeve and tube; said respective crimps each includingradially outwardly divergent portions at the respective opposite ends ofsaid circumferentially extending crimps; said crimps being arrangeddiametrically opposite each other to provide a crimp formation of lemonshape when viewed in transverse cross-section in a plane transverse tothe longitudinal axis of said respective sleeve and tube.
 14. Thecrimped sleeve to tube joint of claim 13, in which said crimps, whenviewed in transverse cross-section taken in a plane which includes thelongitudinal axis of said respective sleeve and tube, extendsymmetrically to opposite sides of a plane transverse to thelongitudinal axis of said respective sleeve and tube, and each includeradially inwardly convergent side faces providing transitions betweenthe outer circumference of said respective sleeve and tube and aradially inner portion of said respective crimps.
 15. The crimped sleeveto tube joint of claim 14, in which said respective inwardly convergentside faces extend on the surface of imaginary cones each having itsperpendicular axis coincident with the longitudinal axis of saidrespective sleeve and tube.
 16. The crimped sleeve to tube joint ofclaim 14, further including axially extending portions of said crimpsproviding a transition between said radially inwardly extending portionsof said crimps.
 17. The crimped sleeve to tube joint of claim 13, inwhich said crimps each include an arcuate portion extending at a fixedradius from the longitudinal axis of said respective sleeve and tube,each said arcuate portion terminating in a straight portion whichextends tangential to said arcuate portion and which terminates at theouter circumference of said respective sleeve and tube at said axiallyextending struts.
 18. The crimped sleeve to tube joint of claim 13, inwhich said axially extending struts each extend on a radius when viewedin cross-section in a plane transverse to the longitudinal axis of saidrespective sleeve and tube which is the same as the radius of theassociated said sleeve and tube when taken at positions spaced from saidcrimps and transverse plane.
 19. The crimped sleeve to tube joint ofclaim 13, including plural said at least two crimps arranged in spacedrelation axially of the longitudinal axis of said respective sleeve andtube.
 20. The crimped sleeve to tube joint of claim 13, in which saidcrimps are of greater length circumferentially of said sleeve and tubethan is the width of said struts circumferentially of said sleeve andtube.
 21. The crimped sleeve to tube joint of claim 13, in which saidcrimps are substantially of U-shaped cross-section and include sidewalls extending in planes inclined relative to each other and converginginwardly towards the longitudinal axis of said respective sleeve andtube.
 22. The crimped sleeve to tube joint of claim 13, in which saidcrimps include radially outwardly divergent walls extending radiallyinwardly toward the longitudinal axis of said respective sleeve andtube.
 23. The crimped sleeve to tube joint of claim 13, in which saidseal ring containing flange includes a radial annular flange engaged atits inner periphery with the outer periphery of said tube, and in whichsaid flange and said crimp are operative to maintain said flange and thecontained seal ring in a compressively stressed condition.
 24. Thecrimped sleeve to tube joint of claim 23, wherein said seal containingflange comprises:flange means including a first annular portion of saidsleeve integral with an axially extending portion of said sleeve, asecond annular portion of said sleeve providing an end of said sleeve,and a radially outwardly extending convex portion of said sleeveproviding a transition between radially outer portions of said first andsecond annular portions; said respective first and second annularportions diverging radially inwardly from said convex portion at equaland opposite angles on opposite sides of a plane transverse to thelongitudinal axis of said respective sleeve and tube; and said seal ringcomprises, an elastomeric seal ring compressively contained within saidflange portion and in continuous surface contact with the inner surfaceof said flange means; an inner radius of said radially outwardly convexportion being of a radius which is 90% of the initial cross-sectionalradius of said radially outer convex portion prior to crimping.
 25. Thecrimped sleeve to tube joint of claim 24, in which said crimp means isspaced axially of said flange means by a distance in excess of theinitial cross-sectional radius of said radially outer convex portion.26. A crimped sleeve to tube joint, including;a tube of circulartransverse cross-section; a sleeve of circular transverse cross-sectiontelescoped over said tube; a seal ring containing flange at one end ofsaid sleeve; a seal ring contained within said seal ring containingflange; said seal ring containing flange having been compressivelyreduced into engagement with the outer circumference of said tube, andsaid sleeve and said tube having been crimped at a location spaced fromsaid one end to immobilize said sleeve against axial and circumferentialmovement relative to said tube, wherein said seal containing flangecomprises: sleeve to tube sealing means provided at said flange meansincluding a first annular portion of said sleeve integral with anaxially extending portion of said sleeve, a second annular portion ofsaid sleeve providing an end of said sleeve, and a radially outwardlyextending convex portion of said sleeve providing a transition betweenradially outer portions of said first and second annular portions; saidrespective first and second annular portions diverging radially inwardlyfrom said convex portion at equal and opposite angles on opposite sidesof a plane transverse to the longitudinal axis of said respective sleeveand tube; and said seal comprises, an elastomeric seal ringcompressively contained within said flange portion and in continuoussurface contact with the inner surface of said flange means; an innerradius of said radially outwardly convex portion being of a radius whichis 90% of the initial cross-sectional radius of said radially outerconvex portion prior to crimping; at least two crimps extending inwardlyof the outer periphery of said respective sleeve and tube, saidrespective crimps being separated from each other circumferentially ofsaid sleeve and tube by struts provided by axially extending portions ofsaid sleeve and tube of the original radius of said respective sleeveand tube, said crimps each being concave inwardly of the outer surfaceof said respective sleeve and tube; said respective crimps eachincluding radially outwardly divergent portions at the respectiveopposite end of said circumferentially extending crimps; said crimps,when viewed in transverse cross-section taken in a plane which includesthe longitudinal axis of said respective sleeve and tube, each extendingsymmetrically to opposite sides of a plane transverse to thelongitudinal axis of said respective sleeve and tube, and each includingradially inwardly convergent side faces providing transitions betweenthe outer circumference of said respective sleeve and tube and aradially inner portion of said respective crimps; said respectiveinwardly convergent side faces each extending on the surface ofimaginary cones each having its perpendicular axis coincident with thelongitudinal axis of said respective sleeve and tube.
 27. The crimpedsleeve to tube joint of claim 26, in which said crimps each include anarcuate portion extending at a fixed radius from the longitudinal axisof said respective sleeve and tube, each said arcuate portionterminating in a straight portion which extends tangential to saidarcuate portion and which terminates at the outer circumference of saidrespective sleeve and tube at said axially extending struts.
 28. Thecrimped sleeve to tube joint of claim 26, including two said crimpsarranged diametrically opposite each other to provide a crimp formationof lemon shape when viewed in section in a plane transverse to thelongitudinal axis of said respective sleeve and tube.
 29. The crimpedsleeve to tube joint of claim 26, in which said axially extending strutseach extend on a radius when viewed in cross-section in a planetransverse to the longitudinal axis of said respective sleeve and tubewhich is the same as the radius of the associated said sleeve and tubewhen taken at positions spaced from said crimps and transverse plane.30. The crimped sleeve to tube joint of claim 26, further includingaxially extending portions of each said crimp providing a transitionbetween said radially inwardly extending portions of said crimps. 31.The crimped sleeve to tube joint of claim 26, including plural said atleast two crimps arranged in spaced relation axially of the longitudinalaxis of said respective sleeve and tube.
 32. The crimped sleeve to tubejoint of claim 26, in which said crimps are of greater lengthcircumferentially of said sleeve and tube than is the width of saidstruts circumferentially of said sleeve and tube.
 33. The crimped sleeveto tube joint of claim 26, in which said crimps are substantially ofU-shaped cross-section and include side walls extending in planesinclined relative to each other and converging inwardly towards thelongitudinal axis of said respective sleeve and tube.
 34. The crimpedsleeve to tube joint of claim 26, in which said crimps include radiallyoutwardly divergent walls extending radially inwardly toward thelongitudinal axis of said respective sleeve and tube.
 35. The crimpedsleeve to tube joint of claim 26, in which said seal ring containingflange includes a radial annular flange engaged at its inner peripherywith the outer periphery of said tube, and in which said flange and saidcrimp are operative to maintain said flange and the contained seal ringin a compressively stressed condition.
 36. The crimped sleeve to tubejoint of claim 26, in which said crimp means is spaced axially of saidflange means by a distance in excess of the initial cross-sectionalradius of said radially outer convex portion.